In the application of printed circuit board (PCB) or flexible printed circuit (FPC), apart from the conventional technique in which copper foil is directly adhered to a substrate, an alternative technique in which polymer permeates the pores of conducting layer has been developed as replacement for copper foil. However, since the surface property of the above-mentioned conducting layer is poor, it is difficult for solder to fully contact the conductive wire, which causes false soldering or even makes it unlikely to solder.